Ground Tissue System Flashcards
What is the role of the ground tissue system?
The ground tissue system provides packaging and support, and holds the plant together.
Which meristem produces ground tissues?
Ground tissues are produced by the ground meristem.
How is the ground tissue system represented in different parts of the plant?
In the leaf, the ground tissue is the mesophyll.
In the stem, ground tissue is the pith and the cortex.
In the root, the ground tissue is the cortex.
Pith vs cortex?
The pith is located inside the vascular bundles at the centre of the plant, the cortex is outside the vascular bundles.
Dicots lack pith in the roots, but root pith is present in monocots.
What are the three main cell types of the ground tissue system? How are their cell walls different?
- Parenchyma: 1° cell wall, most common type
- Collenchyma: thickened 1° wall.
- Sclerenchyma: lignified 2° wall.
What are the characteristics of parenchyma tissue?
- Most common cell in the plant body
- Living tissue
- Make up the soft parts of the plant: cortex, pith, leaf mesophyll, flesh of fruits
- Important for wound response because…
- -> Retain some meristematic ability (capable of cell div)
- -> Are relatively undifferentiated
- -> Usually spherical, may stretch into quadrilateral to fill gaps.
- May be continuous masses or horizontal (rays in 2°) or vertical strands (1° or 2°).
What are the functions of parenchyma tissue?
- Support (provide turgor pressure)
- -> Plants take in water into vacuole for support, giving turgor instead of a 2° cw, like balloon of water. - Storage (e.g. soils, starch, sugar). In succulents, specialised for water storage.
- Regeneration and wound response
- -> Retain meristematic ability, can divide and redifferentiate into new type of tissue. Why if you take cuttings you can get roots growing from stem.
What is plasmolysis?
Plasmolysis describes how when plants wilt they lose turgor by water loss.
What are the types of parenchyma cell?
The three types of parenchyma cell are…
- Aerenchyma
- Chlorenchyma
- Transfer cells
- Aerenchyma are specialised for bouyancy
- -> Have large and abundant intercellular spaces between star-shaped cells. Useful for aeration of root in aquatic and wetland environments,
- Chlorenchyma are specialised for p/s
- -> Have chloroplasts
- Transfer cells are specialised for movement of solutes
- -> Have cell wall ingrowths; infoldings of plasma membrane to increase surface area, are associated with phloem and glandular structures. Good for intensive short distance movement. Associated with vascular tissue, reproductive and glandular structures.
What’s the difference between spongy and palisade chlorenchyma?
- Palisade; tight-packed columns. Usually on top of leaf.
- Spongy: less tight-packed to allow gas exchange through stomata. Usually on bottom of leaf (by locating stomata on bottom this reduces water loss through transpiration.
Functions and characteristics of collenchyma?
- Have unevenly thickened 1° cw: are stronger than parenchyma but unlike sclerenchyma can elongate and stretch bc they are not lignified with a 2° cw so are less rigid, so are ideal to support young, growing plants
- Have a metabolic cost but not so much as sclerenchyma. Still, won’t produce unless necessary; investment for extra thickening.
- Living tissue
- Often elongated.
- Usually outside of the parenchyma tissue, beneath epidermis.
- May form discrete strands or continuous cylinders beneath epidermis in stems or petioles, or bordering eudicot leaf veins.
What are bast fibres?
- Bast fibres are collenchyma tissue fibres found in phloem area and bundle cap, derived from eudicot stems. Schlerenchyma tissue.
Functions and characteristics of sclerenchyma?
- Lignified, rigid cells with 2° cw at high metabolic cost. - Cannot elongate; found in parts of cell that have stopped growing
- Support and protection
- Often dead at maturity; unable to divide, meristematic ability lost.
- May occur singly (idioblasts) or form continuous masses of tissue.
- In both primary and secondary plant body
- May form in large groups as tissue, small groups or individually.
What are the two types of sclerenchyma tissue?
The two types of sclerenchyma tissue are
- Sclereids
- Fibres
What the different types of sclereids?
- Osteosclereids (bone-shaped) provide support around leaves/stem
- Macrosclereids (column-shaped) make hard outer shell
- Astersclereids (star-shaped) make leaves tougher but still bendy
- Brachysclereids (stone-cells)
